1. Field of the Invention
The present invention relates to an apparatus for forming, punching and stacking deep-drawn articles of thermoplastic synthetic material or the like. The apparatus includes a heating unit, an intermittent foil transporting unit, a rigid upper tool, and a raisable and lowerable as well as pivotable lower tool, wherein the movements of the lower tool are determined by cam discs mounted on a drive shaft and by cam rollers for the cam discs, and a stacking device.
2. Description of the Related Art
A thermoforming machine of the above-described type is disclosed in DE-C2 33 46 628. In a machine of this type, articles of synthetic materials, such as, margarine containers, drinking cups, container covers, etc., are produced between the tools which can be moved toward each other and apart from each other. The articles are formed in the closed position of the upper and lower tools, the articles are then punched and transported out of the tool in the open position into a stacking device. The upper tool or upper component of this known thermoforming machine is mounted on a rigid transverse bridge, while the lower tool or component is fastened to a vertically movable and pivotable forming table. For making the forming table pivotable, the forming table has bearing pins whose bearings are each arranged in a vertically guided guide piece. The drive is effected by toggle levers which rest with cam rollers against cam discs mounted on a main shaft.
The toggle lever mechanism composed of various lugs for pivoting the entire pivoting table with the lower tool mounted thereon in a vertical guide means which is not pivoted, is very complicated. To ensure that the articles do not come into contact with interfering edges during stacking, such as in the area of the foil transporting unit, a large pivoting angle of approximately 45-90.degree., typically, 80.degree. is required. The articles which are ejected almost horizontally in this case, must be received in a moving stacking plate which is moved against the lower tool, because otherwise there would be the danger that the articles drop too far downwardly as a result of gravity on their way into the stacking plate and would not be able to enter the stacking plate openings. Not very helpful is another alternative with a stacking plate which is located deeper already from the outset, because in this case articles could change their trajectory angles on their way to the stacking plate.
Finally, an alternative embodiment in which the articles are moved toward the ejector by suction has the disadvantage that the ejector becomes more complicated and also more expensive because of the vacuum plant which would have to be provided. The large pivoting angle of the known thermoforming machine required for the entire pivoting table further makes it necessary to provide expensive rotary-type connections for the cooling water line into the lower water tool, wherein these connections result in significant sealing problems and, thus, maintenance operations.